Various stroke training devices for tennis are known which connect a user's wrist to the grip of a tennis racket. Examples of such devices are shown in U.S. Pat. Nos. 3,858,881; 4,150,821; 4,209,169; and 4,445,686. Such devices are used to teach a proper wrist position during stroking. One consequence of such training is to reduce tennis elbow. While suitable for their intended purpose, such stroke training devices do not provide training which will conform a tennis swing to the force generating capabilities of a properly rotating body swinging motion.
U.S. Pat. Nos. 3,937,465 and 4,030,732 disclose harness devices for controlling a tennis swing to prevent a tennis racket from shifting in a vertical plane below the wrist of a user. While the devices will train part of a tennis swing, they do not provide a device which will transmit and focus body rotation forces at the grip of a tennis racket so as to increase centrifugal forces at the head of the tennis racket.
Many other stroke training devices have been proposed for use in grooving a golf swing. U.S. Pat. Nos. 1,962,256; 2,022,910; 2,498,006; 3,188,090; and 3,804,420 are examples of such devices in which the golfers are restrained to prevent over swinging with the right hand in the case of a right handed golfer (the reverse with a left handed golfer). While suitable for their intended purpose, the devices do not train a golfer to focus the rotation energy of his body at the point which the club head will impact a ball during striking motion.
Another group of stroke training devices for golf include harness devices for preventing head lift during swinging (U.S. Pat. No. 4,134,589); a tension device that will signal the user so that the user will feel departures from a proper swing pattern (U.S. Pat. No. 4,662,640); devices which will produce an audible signal when the golf swing is improper (U.S. Pat. No. 3,680,869); an elbow swing control device to prevent casting of the elbow during the backswing (U.S. Pat. No. 3,804,420); and a device which will hold the club grip and apply a force on the user's hands so as to train against the user rearing up either immediately prior to striking of the ball or immediately following striking of the ball (U.S. Pat. No. 4,479,653). None of the aforesaid stroke training devices are configured or arranged to train a golfer to properly focus the force of body rotation at the user's hands for extension to the point of striking the ball.
One problem with prior art stroking devices is that they do not provide for proper application of the forces of body rotation at the point of object impact.